# 二叉树的最小深度

## LeetCode 111. 二叉树的最小深度

### 题目

[111](https://leetcode-cn.com/problems/minimum-depth-of-binary-tree/)

```
给定一个二叉树，找出其最小深度。

最小深度是从根节点到最近叶子节点的最短路径上的节点数量。

说明：叶子节点是指没有子节点的节点。



示例 1：


输入：root = [3,9,20,null,null,15,7]
输出：2
示例 2：

输入：root = [2,null,3,null,4,null,5,null,6]
输出：5
```

### 题解

#### BFS

```javascript
var minDepth = function(root) {
    if(root == null) return 0;

    const queue = [];
    let depth = 1;

    queue.push(root);

    while(queue.length !== 0){
        const len = queue.length;
        for(let i=0;i<len;i++){
            const curr = queue.shift();
            if(curr.left == null && curr.right == null){
                return depth;
            }
            if(curr.left) queue.push(curr.left);
            if(curr.right) queue.push(curr.right);
        }
        depth++;
    }
};
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://voyz.gitbook.io/voyz-algorithm/bfs/er-cha-shu-de-zui-xiao-shen-du.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.